Creagrutus occidaneus Vari & Harold 2001

Creagrutus occidaneus

DIAGNOSIS.—The combination of the possession of premaxillary dentition arranged in the three components generalized for most of the species of Creagrutus and Piabina without a distinctly larger gap between the first and second teeth of the primary series, 3 or 4 teeth on the maxilla, 6, rarely 5, teeth in the primary tooth row of the premaxilla, 4 or 5 dentary teeth, 38 to 43 lateral line scales without a lamellar process over each pore, 9 or 10 predorsal median scales, 3 or 4 scale rows between the dorsal-fin origin and the lateral line, 37 to 39 vertebrae, 10 or 11 branched anal-fin rays, 2 post-anal median scales to the anal-fin origin, 6 to 8 gill rakers on the upper limb of the first gill arch, 11 to 13 gill rakers on the lower limb of the first gill arch, the bony orbital diameter (32.6%–37.9% of HL), the anal-fin length (15.9%–19.5% of SL), the distance from the dorsal-fin origin to the anal-fin origin (30.3%–36.0% of SL), the distance from the dorsal-fin origin to the pelvic-fin insertion (25.4%–30.8% of SL), the distance from the dorsal-fin origin to the pectoral-fin insertion (30.9%–35.8% of SL), the caudal peduncle depth (10.9%–12.8% of SL), the head length (24.1 %–27.7% of SL), the postorbital length (41.0%–46.1% of HL), the interorbital width (29.9%–32.9% of HL), the well-developed third infraorbital approaching, or in some specimens contacting, the horizontal limb of the preopercle, the lack of a series of dark midlateral spots on the body, the vertically elongate, ventrally tapering humeral mark, the lack of a large spot of pigmentation on the basal portions of the middle caudal-fin rays, and the absence of a discrete patch of dark pigmentation on the middle portion of the anterior dorsal-fin rays distinguishes Creagrutus occidaneus within the clade compose of Creagrutus and Piabina.

Characters A B

Morphometrics

Standard length 60.4 26.8–65.9

1. Snout to anal-fin origin 62.9 61.8–69.2

2. Snout to pelvic-fin insertion 45.5 44.3–51.0

3. Snout to pectoral-fin insertion 24.2 23.0–26.8

4. Snout to dorsal-fin origin 44.2 44.1–49.5

5. Dorsal-fin origin to hypural joint 60.4 55.3–60.7

6. Dorsal-fin origin to anal-fin origin 32.3 30.3–36.0

7. Dorsal-fin origin to pelvic-fin insertion 27.6 25.4–30.8

8. Dorsal-fin origin to pectoral-fin insertion 31.3 30.9–35.8

9. Caudal peduncle depth 11.1 10.9–12.8

10. Pectoral-fin length 19.3 19.0–22.2

11. Pelvic-fin length 15.9 13.6–17.0

12. Dorsal-fin length 21.2 20.1–25.7

13. Anal-fin length 17.1 15.9–19.5

14. Head length 26.2 24.1–27.7

15. Postorbital head length 45.6 41.0–46.1

16. Snout length 26.6 25.5–30.9

17. Bony orbital diameter 33.4 32.6–37.9

18. Interorbital width 30.0 29.9–32.9

Meristics

Lateral line scales 42 38–43

Scale rows between dorsal-fin origin and lateral line 4 3–41

Scale rows between anal-fin origin and lateral line 3 3

Predorsal median scales 10 9–10

Branched dorsal-fin rays 8 8

Branched anal-fin rays 11 10–11

Branched pelvic-fin rays 6 6

Pectoral-fin rays 13 12–13

Vertebrae 39 37–39

1Three scales between anal-fin origin and lateral line present in only 1 of 27 paratypes.

DESCRIPTION.—Morphometric and meristic data for Creagrutus occidaneus in Table 40. Head moderately robust, body ranging from moderately elongate in some mature males to relatively robust in gravid females. Greatest body depth typically at dorsal-fin origin, but shifted anterior of that point in some gravid females. Dorsal profile of head gently convex from tip of snout to vertical through posterior nostril, straight from that point to tip of supraoccipital spine. Interorbital region slightly convex transversely. Predorsal profile straight and continuous with dorsal profile of body in smaller individuals, becoming slightly convex, with variably distinct change in alignment relative to profile of head in larger specimens. Dorsal surface of body with distinct median ridge extending anteriorly from dorsal-fin insertion approximately one-half of distance to tip of supraoccipital spine. Ventral profile of head with obvious obtuse angle at anteroventral corner of dentary, nearly straight from that angle to rear of isthmus. Ventral profile of body ranging from nearly straight in smaller specimens and mature males to distinctly convex in gravid females. Prepelvic region of body obtusely flattened transversely.

Head somewhat pointed in lateral view, more so in dorsal view. Upper jaw not very fleshy, longer than, and distinctly overhanging, lower jaw. Snout not very fleshy, with scattered papillae anteromedially; papillae concentrated along upper lip and on folds and plicae extending between outer and medial premaxillary teeth. Lower jaw fleshy, more so anteriorly, with numerous papillae on dorsal margin of lip and scattered papillae on anterior surface of jaw.

Infraorbital series moderately well developed. Anterior one-half of ventral margin of third infraorbital falling slightly short of or, more rarely, contacting horizontal limb of preopercle. Posterior margins of third through fifth infraorbitals falling distinctly short of vertical limb of preopercle.

Premaxillary dentition in three series: primary row typically consisting of 6, sometimes 5, teeth arranged in nearly straight to slightly sigmoid series without pronounced gap between first and second tooth of series; triangular cluster of slightly larger teeth with posterolateral tooth largest; and typically single tooth of form similar to that of primary series lying lateral to fourth tooth of primary premaxillary series, or lateral to area of contact of third and fourth teeth of primary series; few specimens with 2 teeth lying lateral to area of contact of fourth tooth with third and fifth teeth respectively. Maxilla with 3 or 4 tricuspidate teeth. Dentary with 4 or 5 tricuspidate teeth; first and second teeth distinctly larger than remaining teeth in series, with second tooth somewhat larger than first tooth; third tooth only approximately one-third vertical extent of second tooth, but about 3 times height of fourth tooth. Fifth tooth, when present, smaller than fourth tooth.

Dorsal-fin rays ii,8 in all examined specimens. Dorsal-fin origin at, or slightly anterior to, vertical through pelvic-fin insertion. Profile of distal margin of dorsal fin slightly concave. Anal-fin rays ii, 10–11. Profile of distal margin of anal fin nearly straight in smaller individuals, increasingly concave in larger specimens. Mature males with hooks occasionally present on last unbranched anal-fin ray and anterior 2 to 4 branched anal-fin rays. Pectoral-fin rays i,11–12. Tip of pectoral fin extending posteriorly slightly over three-fourths of distance to pelvic-fin insertion. Pelvic-fin rays i,6,i. Tip of pelvic fin extending posteriorly to, or falling slightly short of, anus. Hooks present on all branched pelvic-fin rays in mature males.

Gill rakers 6–8 + 11–13.

COLORATION IN ALCOHOL.—Ground color of specimens in alcohol tan. Dorsal surface of head with scattered field of small superficial dark chromatophores and obscure field of deep-lying, very dark chromatophores overlying membranes of brain. Chromatophore field more concentrated anteriorly on head, over snout, and on portions of upper lip. Region of snout anterior to nostrils with concentrated chromatophores forming dark, crescent-shaped patch continuous posteroventrally with narrow band of dark chromatophores extending along ventral and posterior margins of orbit. Dorsal portions of opercle and all infraorbitals posterior to orbit with scattered, dark chromatophores. Dark pigmentation on head obscured by surface guanine layer in many specimens.

Scales of dorsal portion of body with diffuse chromatophore field on basal portions of exposed field and some scattered chromatophores along distal margin resulting in dark, reticulate pigmentation pattern on those portions of body. Humeral mark prominent, distinctly tapering ventrally, extending ventrally approximately one-half of scale below lateral line and dorsally about two scales above lateral line. Margins of humeral mark somewhat variable, but distinct dorsally. Diffuse midlateral band formed of small, dark chromatophores extending from slightly posterior of humeral mark to middle of caudal peduncle.

Dorsal fin with anterior margin of last unbranched ray and basal portions of branched fin rays outlined by dark chromatophores. Membranes of anterior rays with scattered, dark chromatophores, extent of chromatophore field more extensive anteriorly. Anal fin with scattered, dark chromatophores on membranes in some individuals. Caudal fin with scattered, light brown chromatophores over membranes and rays. Pectoral and pelvic fins hyaline.

ETYMOLOGY.—The specific name, occidaneus, from the Latin for western, refers to the distribution of the species along the western lowlands of the Amazon basin.

ECOLOGY.—The type locality was a white-water rainforest stream with a sandy bottom at an elevation of approximately 325 m. Other Peruvian localities for which habitat data is available had similar water conditions with substrates of mixed rubble, silt, sand, gravel, and clay. These localities ranged between 190 and 290 m elevation.

SEXUAL DIMORPHISM.—The examined samples of Creagrutus occidaneus apparently do not demonstrate the distinct size difference between mature males and females found in many members of the genus. Mature males, as shown by the presence of well-developed hooks on the anal and pelvic fins, ranged from 38.6 to 61.1 mm SL, whereas females measured up to only 65.9 mm SL.

DISTRIBUTION.—Creagrutus occidaneus is distributed across the foothills and lowlands of eastern Peru in the Río Manu basin of the Department of Madre de Dios and in the upper Rio Purus basin in the states of Acre and Amazonas, Brazil, and the Department of Ucayali, Peru (Figure 67, dots).

MATERIAL EXAMINED.—183 specimens (33, 26.8–65.9).

HOLOTYPE.—PERU. Madre de Dios: Provincia Manu, Parque Nacional Manu, Pakitza, beach along Río Manu close to mouth of Quebrada Pachija (approximately 11°57′S, 71°17′W), collected by H. Ortega and F. Pinares, 9 Oct 1991, MUSM 8869, 1 (60.4).

PARATYPES.—27 specimens (27, 26.8–65.9).

PERU. Madre de Dios: Provincia Manu, Parque Nacional Manu, Pakitza, beach along Río Manu close to mouth of Quebrada Pachija (approximately 11°57′S, 71°17′W), collected with holotype, MUSM 8870, 4 (26.8–63.9); USNM 326920, 7 (38.3–65.9; 2 specimens cleared and counterstained for cartilage and bone). Provincia Manu, mouth of Rio Pinquen, near Boca Manu (12°10′S, 71°01′W), collected by R. Horwitz, 4 Aug 1977, ANSP 143765, 1 (61.3). Provincia Manu, Río Manu, approximately 2 hours by boat upstream from Boca Manu, collected by H. Ortega et al., 7 Sep 1988, USNM 303065, 1 (50.7). Provincia Manu, Parque Nacional Manu, Pakitza and vicinity (approximately 11°57′S, 71°17′W), collected by H. Ortega, Oct 1987, USNM 295621, 9 (49.0–61.8); MUSM 8871, 5 (29.9–56.1).

NONTYPE SPECIMENS.—155 specimens (5, 46.8–60.5).

PERU. Madre de Dios: Provincia Manu, Parque Nacional Manu, Pakitza and vicinity (approximately 11°57′S, 71°17′W), USNM 295571, 5 (46.8–60.5). Provincia Manu, Parque Nacional Manu, Río Manu, near mouth of Quebrada Fortaleza, USNM 319661, 1. Provincia Manu, Parque Nacional Manu, Pakitza, Quebrada Fortaleza, USNM 326875, 2. Provincia Manu, Parque Nacional Manu, Río Manu, Quebrada Fortaleza, 15 m above mouth, USNM 319657, 1. Provincia Manu, Parque Nacional Manu, Río Manu at Pakitza, USNM 302789, 3; USNM 302787, 4. Provincia Manu, Parque Nacional Manu, Pakitza, Quebrada Pachija (approximately 11°57′, 71°17′W), USNM 326818, 5. Provincia Manu, Río Manu, approximately 2 hours by boat upstream from Boca Manu, USNM 303064, 2. Provincia Manu, Boca Panahua, where Quebrada Panahua enters Río Manu, USNM 302790, 1. Provincia Manu, Río Manu, approximately 3 hours upriver by boat from Romero, USNM 302784, 3. Provincia Manu, cocha off Río Alto Madre de Dios, 2 km below Erika (latter locality at approximately 12°53′S, 71°12′W), USNM 302786, 2. Provincia Manu, Río Alto Madre de Dios, 15 km upstream from Boca Manu (12°19′30″S, 70°58′W), ANSP 143768, 1. Ucayali: Provincia Purus, Río Curanja basin, Caserío Grau (9°58′S, 71°02′W), MUSM 9986, 2. Provincia Purus, Río Purus (9°50′S, 70°55′W), MUSM 10440, 6. Provincia Purus, Esperanza, Quebrada Esperancillo (9°42′S, 70°40′W), MUSM 10032, 15. Atalaya, Sepahua, Quebrada Shamboyacu, USNM 358016, 13. Atalaya, Sepahua, Nuevo Horizonte, Río Bajo Urubamba, USNM 358017, 21.

BRAZIL. Acre: Rio Acre between Seringal Paraiso and Lago Amapá, MZUSP 49760, 2. Município de Rio Branco, Rio Acre, Coloação do Chalé 6 hours below Rio Branco (latter locality at 9°58′S, 67°48′W), MZUSP 49625, 5. Amazonas: Rio Acre, Seringal Floresta, 10 minutes above Boca do Acre (latter locality at 8°45′S, 67°23′W), MZUSP 49600, 44. Rio Purus, at mouth of Rio Acre (8°45′S, 67°23′W), MZUSP 49708, 10. Município de Porto Acre, Rio Acre, Seringal Bom Destino, 1 hour above Porto Acre (latter locality at 9°34′S, 67°31′W), MZUSP 49688, 7.